_ Git - BearSSL/blob - src/symcipher/chacha20_ct.c

   1 /*
   2  * Copyright (c) 2016 Thomas Pornin <pornin@bolet.org>
   3  *
   4  * Permission is hereby granted, free of charge, to any person obtaining
   5  * a copy of this software and associated documentation files (the
   6  * "Software"), to deal in the Software without restriction, including
   7  * without limitation the rights to use, copy, modify, merge, publish,
   8  * distribute, sublicense, and/or sell copies of the Software, and to
   9  * permit persons to whom the Software is furnished to do so, subject to
  10  * the following conditions:
  11  *
  12  * The above copyright notice and this permission notice shall be
  13  * included in all copies or substantial portions of the Software.
  14  *
  15  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  16  * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  17  * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  18  * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
  19  * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
  20  * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
  21  * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  22  * SOFTWARE.
  23  */
  24
  25 #include "inner.h"
  26
  27 /* see bearssl_block.h */
  28 uint32_t
  29 br_chacha20_ct_run(const void *key,
  30         const void *iv, uint32_t cc, void *data, size_t len)
  31 {
  32         unsigned char *buf;
  33         uint32_t kw[8], ivw[3];
  34         size_t u;
  35
  36         static const uint32_t CW[] = {
  37                 0x61707865, 0x3320646e, 0x79622d32, 0x6b206574
  38         };
  39
  40         buf = data;
  41         for (u = 0; u < 8; u ++) {
  42                 kw[u] = br_dec32le((const unsigned char *)key + (u << 2));
  43         }
  44         for (u = 0; u < 3; u ++) {
  45                 ivw[u] = br_dec32le((const unsigned char *)iv + (u << 2));
  46         }
  47         while (len > 0) {
  48                 uint32_t state[16];
  49                 int i;
  50                 size_t clen;
  51                 unsigned char tmp[64];
  52
  53                 memcpy(&state[0], CW, sizeof CW);
  54                 memcpy(&state[4], kw, sizeof kw);
  55                 state[12] = cc;
  56                 memcpy(&state[13], ivw, sizeof ivw);
  57                 for (i = 0; i < 10; i ++) {
  58
  59 #define QROUND(a, b, c, d)   do { \
  60                 state[a] += state[b]; \
  61                 state[d] ^= state[a]; \
  62                 state[d] = (state[d] << 16) | (state[d] >> 16); \
  63                 state[c] += state[d]; \
  64                 state[b] ^= state[c]; \
  65                 state[b] = (state[b] << 12) | (state[b] >> 20); \
  66                 state[a] += state[b]; \
  67                 state[d] ^= state[a]; \
  68                 state[d] = (state[d] <<  8) | (state[d] >> 24); \
  69                 state[c] += state[d]; \
  70                 state[b] ^= state[c]; \
  71                 state[b] = (state[b] <<  7) | (state[b] >> 25); \
  72         } while (0)
  73
  74                         QROUND( 0,  4,  8, 12);
  75                         QROUND( 1,  5,  9, 13);
  76                         QROUND( 2,  6, 10, 14);
  77                         QROUND( 3,  7, 11, 15);
  78                         QROUND( 0,  5, 10, 15);
  79                         QROUND( 1,  6, 11, 12);
  80                         QROUND( 2,  7,  8, 13);
  81                         QROUND( 3,  4,  9, 14);
  82
  83 #undef QROUND
  84
  85                 }
  86                 for (u = 0; u < 4; u ++) {
  87                         br_enc32le(&tmp[u << 2], state[u] + CW[u]);
  88                 }
  89                 for (u = 4; u < 12; u ++) {
  90                         br_enc32le(&tmp[u << 2], state[u] + kw[u - 4]);
  91                 }
  92                 br_enc32le(&tmp[48], state[12] + cc);
  93                 for (u = 13; u < 16; u ++) {
  94                         br_enc32le(&tmp[u << 2], state[u] + ivw[u - 13]);
  95                 }
  96
  97                 clen = len < 64 ? len : 64;
  98                 for (u = 0; u < clen; u ++) {
  99                         buf[u] ^= tmp[u];
 100                 }
 101                 buf += clen;
 102                 len -= clen;
 103                 cc ++;
 104         }
 105         return cc;
 106 }